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Behavior and Ethology

Abstract

This research is concerned with whether animals integrate multiple prior fighting experiences into behavioral decisions in subsequent contests. The effect of prior fighting experience on behavior of contestants at different stages of a contest was examined. Further, a probability model of integrating fighting experiences into current aggressive behavior was proposed and tested.

Rivulus marmoratus, an internally self-fertilization hermaphroditic fish, has been repeatedly observed to display aggressive behavior in both field and laboratory, and thus was selected for this research. However, their contest behavior has never been described before. This project started with observing and comparing their behavior in both dyadic contests and mirror tests. Different clones did not behave differently in either test, but the two tests yielded different conclusions regarding the aggressiveness of different clones.

The fish were given different combinations of two prior fighting experiences to investigate how different prior fighting experiences were evaluated. The major conclusions are: (1) the effect of the most recent experience was more pronounced than the effect of the penultimate fighting experience; (2) the primary effect of the two experiences did not come from a potential damage asymmetry due to different prior fighting experiences; and (3) the changes in contest behaviors were consistent with the hypothesis that prior fighting experiences influence how an individual perceives its relative fighting ability but do not influence its actual relative fighting ability in subsequent contests. These results were used to develop a model that combines the effect of past experiences of two individuals to predict the probability of winning a dyadic contest. The model parameters were estimated with experimental data and correctly predicted the outcome of contests. These results indicate that the effects from past fighting experiences are accumulated systematically and that the relative past experiences of two contestants determine the outcome of their interaction when other factors are controlled. They also suggest that the fish offers a model system for examining how experiences are integrated into current decisions. Although the model was developed for animal contests, its general approach to integrating prior experiences for different individuals might be useful for understanding other interactions that are affected by learning.